Nacelle air scoop assembly

ABSTRACT

An air scoop assembly that may be for a nacelle of a turbofan engine includes a surface defining at least in-part a primary flowpath and a hood formed to the surface and projecting into the primary flowpath. The hood includes a distal, leading, edge that is irregular in shape thereby producing air vortices that shed from the leading edge and co-extend in a downstream direction with an airstream in the primary flowpath. The vortices are thereby controlled such that air flow disruption and undesired resonance is minimized or eliminated.

This application claims priority to U.S. Patent Appln. No. 62/013,880filed Jun. 18, 2014.

BACKGROUND

The present disclosure relates to gas turbine engines, and moreparticularly to an air scoop assembly in a nacelle of the gas turbineengine and method of operating.

Air scoops are known to project into a primary air flowpath forredirecting a portion of the air flow to serve a particular purpose suchas cooling of components in a remote region. One example of such airscoops are those that project into a bypass air flowpath of a nacellefor a turbofan engine often called ram scoops. Unfortunately, the airscoops are known to disrupt efficient airstream flow. This disruption isfurther aggravated where air scoop assemblies include valves thatintermittently limit or prevent diversion of air flow through the airscoop assembly.

For example, with a valve of the air scoop assembly closed, flow spillsaround the ram scoop and tends to separate off a leading edge of thescoop or hood. With traditional, uniform, edge contours, this separationmay result in the shedding of a coherent vortex spanning the full widthof the ram scoop. This type of shedding may couple with the naturalfrequency of the ducting between the ram scoop inlet lip and the valvecontrolling the flow. This resonance may produce significant unsteadypressures resulting in elevated noise and/or elevated unsteady stressesin surrounding structures.

SUMMARY

An air scoop assembly configured to mount to a surface defining aprimary flow path, the assembly according to one, non-limitingembodiment of the present disclosure includes a hood having an irregularupstream edge and configured to project into the primary flowpath.

Additionally to the foregoing embodiment, the edge is at least onevortex generator.

In the alternative or additionally thereto, in the foregoing embodiment,the edge is scalloped.

In the alternative or additionally thereto, in the foregoing embodimentthe air scoop assembly includes an air duct having an inlet defined atleast by the surface and the edge.

In the alternative or additionally thereto, in the foregoing embodiment,the air duct defines a secondary flowpath in fluid communication withthe primary flowpath and for the intermittent flow of air from theprimary flowpath.

In the alternative or additionally thereto, in the foregoing embodimentthe air scoop assembly includes a valve configured for the intermittentisolation of the secondary flowpath.

In the alternative or additionally thereto, in the foregoing embodiment,the valve includes a closed position and an open position and the atleast one vortex generator forms at least one vortex that breaks up anycoherent shedding off of air flow from the hood when the valve is in theclosed position.

In the alternative or additionally thereto, in the foregoing embodiment,the edge has at least one apex projecting in an upstream direction andinto the primary flowpath.

In the alternative or additionally thereto, in the foregoing embodiment,the edge has at least one apex projecting into an upstream direction andinto the primary flowpath.

In the alternative or additionally thereto, in the foregoing embodiment,the hood is flush with the surface.

In the alternative or additionally thereto, in the foregoing embodiment,the hood projects transversely into the primary flowpath and outwardfrom the surface.

In the alternative or additionally thereto, in the foregoing embodiment,the surface is carried by a nacelle.

In the alternative or additionally thereto, in the foregoing embodiment,the apex projects upstream by a downstream-most portion of the edge by adistance that is about twice a thickness of the hood.

In the alternative or additionally thereto, in the foregoing embodiment,the at least one apex is spaced from a next adjacent apex by a distancethat is about one fifth to about one half a height of the hood.

A nacelle for a gas turbine engine according to another, non-limiting,embodiment includes a fan cowling concentrically disposed to an engineaxis and surrounding a fan section of the gas turbine engine; a corecowling concentrically disposed to the engine axis and locateddownstream of the fan section with an annular air bypass flowpathdefined between and by the fan and core cowlings; and a hood formed tothe core cowling and projecting into the bypass flowpath, the hoodincluding a leading edge that includes at least one apex projecting inan upstream direction and acting as at least one vortex generator.

Additionally to the foregoing embodiment, the nacelle includes an airduct having an inlet defined at least by the core cowling and the edge;and wherein the air duct defines a secondary flowpath in fluidcommunication with the bypass flowpath and for the intermittent flow ofair from the bypass flowpath.

In the alternative or additionally thereto, in the foregoing embodimentthe nacelle includes a valve in the air duct for the intermittentisolation of the secondary flowpath; and wherein the valve includes aclosed position and an open position and the at least one vortexgenerator forms at least one vortex that breaks up any coherent sheddingoff of air flow from the hood when the valve is in the closed position.

In the alternative or additionally thereto, in the foregoing embodiment,the hood is flush with the core cowling.

In the alternative or additionally thereto, in the foregoing embodiment,the hood projects transversely into the bypass flowpath and radiallyoutward from the core cowling.

A method of operating an air scoop assembly according to another,non-limiting, embodiment includes the steps of substantially closing theair scoop assembly having a hood that projects into a primary airflowpath; and forming at least one air vortex that stems from anirregular leading edge of a hood of the air scoop assembly and extendsin a substantially downstream direction thereby minimizing disruption ofairstreams in the primary air flowpath.

The foregoing features and elements may be combined in variouscombination without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, the following descriptionand figures are intended to exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limitingembodiments. The drawings that accompany the detailed description can bebriefly described as follows:

FIG. 1 is a schematic cross section of a gas turbine engine;

FIG. 2 is a partial perspective view of the engine viewing in anupstream direction;

FIG. 3 is a side view of an air scoop assembly;

FIG. 4 is a perspective view of a hood of the air scoop assembly; and

FIG. 5 is a cross section of a leading edge of the hood taken along line5-5 of FIG. 4.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20 disclosed as atwo-spool turbo fan that generally incorporates a fan section 22, acompressor section 24, a combustor section 26 and a turbine section 28.The fan section 22 drives air along a bypass or primary flowpath 29while the compressor section 24 drives air along a core flowpath forcompression and communication into the combustor section 26 thenexpansion through the turbine section 28. Although depicted as aturbofan in the disclosed non-limiting embodiment, it should beunderstood that the concepts described herein are not limited to usewith turbofans as the teachings may be applied to other types of turbineengine architecture such as turbojets, turboshafts, three-spoolturbofans, land-based turbine engines, and others.

The engine 20 generally includes a low spool 30 and a high spool 32mounted for rotation about an engine axis A via several bearingstructures 38 and relative to a static engine case 36. The low spool 30generally includes an inner shaft 40 that interconnects a fan 42 of thefan section 22, a low pressure compressor 44 (“LPC”) of the compressorsection 24 and a low pressure turbine 46 (“LPT”) of the turbine section28. The inner shaft 40 drives the fan 42 directly, or, through a gearedarchitecture 48 to drive the fan 42 at a lower speed than the low spool30. An exemplary reduction transmission may be an epicyclictransmission, namely a planetary or star gear system.

The high spool 32 includes an outer shaft 50 that interconnects a highpressure compressor 52 (“HPC”) of the compressor section 24 and a highpressure turbine 54 (“HPT”) of the turbine section 28. A combustor 56 ofthe combustor section 26 is arranged between the HPC 52 and the HPT 54.The inner shaft 40 and the outer shaft 50 are concentric and rotateabout the engine axis A. Core airflow is compressed by the LPC 44 thenthe HPC 52, mixed with the fuel and burned in the combustor 56, thenexpanded over the HPT 54 and the LPT 46. The LPT 46 and HPT 54rotationally drive the respective low spool 30 and high spool 32 inresponse to the expansion.

In one non-limiting example, the gas turbine engine 20 is a high-bypassgeared aircraft engine. In a further example, the gas turbine engine 20bypass ratio is greater than about six (6:1). The geared architecture 48can include an epicyclic gear train, such as a planetary gear system orother gear system. The example epicyclic gear train has a gear reductionratio of greater than about 2.3:1, and in another example is greaterthan about 2.5:1. The geared turbofan enables operation of the low spool30 at higher speeds that can increase the operational efficiency of theLPC 44 and LPT 46 and render increased pressure in a fewer number ofstages.

A pressure ratio associated with the LPT 46 is pressure measured priorto the inlet of the LPT 46 as related to the pressure at the outlet ofthe LPT 46 prior to an exhaust nozzle of the gas turbine engine 20. Inone non-limiting example, the bypass ratio of the gas turbine engine 20is greater than about ten (10:1); the fan diameter is significantlylarger than the LPC 44; and the LPT 46 has a pressure ratio that isgreater than about five (5:1). It should be understood; however, thatthe above parameters are only exemplary of one example of a gearedarchitecture engine and that the present disclosure is applicable toother gas turbine engines including direct drive turbofans.

In one non-limiting example, a significant amount of thrust is providedby the bypass flowpath 29 due to the high bypass ratio. The fan section22 of the gas turbine engine 20 is designed for a particular flightcondition—typically cruise at about 0.8 Mach and about 35,000 feet(10,668 meters). This flight condition, with the gas turbine engine 20at its best fuel consumption, is also known as Thrust Specific Fuelconsumption (TSFC). TSFC is an industry standard parameter of fuelconsumption per unit of thrust.

Fan Pressure Ratio is the pressure ratio across a blade of the fansection 22 without consideration of the effect of a fan exit guide vaneassembly 58 located downstream of the fan 42 (also see FIG. 2). The lowFan Pressure Ratio according to one, non-limiting, example of the gasturbine engine 20 is less than 1.45:1. Low Corrected Fan Tip Speed isthe actual fan tip speed divided by an industry standard temperaturecorrection of (T/518.7^(0.5)), where “T” represents the ambienttemperature in degrees Rankine. The Low Corrected Fan Tip Speedaccording to one non-limiting example of the gas turbine engine 20 isless than about 1150 fps (351 m/s).

Referring to FIGS. 1 and 2, a nacelle assembly 60 of the turbine engine20 has core cowling 62, a fan cowling 64 and a pylon 66. The core andfan cowlings 62, 64 are generally concentric to the engine axis A withthe core cowling 62 generally supporting the core engine and surroundingthe engine sections 24, 26, 28. The fan cowling 64 is spaced radiallyoutward from the core cowling 62 and surrounds the fan 42 and guide vaneassembly 58. The annular bypass flow path 29 is defined between and bythe core and fan cowlings 62, 64. The pylon 66 may be attached to bothcowlings 62, 64 and generally supports and attaches the entire engine 20to, for example, an aircraft (not shown).

Referring to FIGS. 1 through 3, an annular engine cavity 68 is locatedradially between and may be defined by the core cowling 62 and the innerengine case 36. Various engine components (not shown) may be generallylocated in the cavity 68 and may require cooling by a ventilation or aircooling system 70 through a series of tube and hoses directed to thecomponent and/or otherwise ventilate the cavity 68 to prevent theaccumulation of fumes. Cooling system 70 may include an air scoopassembly 72 having a hood 74 mounted to the core cowling 62 (as oneexample) and projecting into the bypass flowpath 29 for receipt of asecondary airflow. In some examples of the cooling system 70, the amountof secondary airflow is dependent mainly upon the pressure differencebetween the bypass flowpath 29 and the ambient air, and other systemsmay include control logic with associated flow control valve(s).

One, non-limiting, example of such an air cooling system 70, is anActive Clearance Control (ACC) cooling system 70 that assists in thecontrol of a blade tip clearance between the engine case 36 and the tipsof the rotating blades of the turbine section 28. More specifically, theACC cooling system 70 adjusts cooling flow to the engine case 36 therebycontrolling thermal expansion of the case relative to centrifugal andthermal expansion of the turbine rotor thereby minimizing and/orcontrolling the blade tip clearance throughout varying engine operatingconditions.

The air scoop assembly 72 of the ACC cooling system 70 includes the hood74, a duct 76 defining a secondary air flowpath 78, and a flow controldevice or at least one valve 80 that intersects the duct 76 forcontrolling the amount of secondary air flow. The hood 74 has acontoured or scalloped leading edge 82 that, with a radially outwardfacing surface 84 of the core cowling 62, defines an inlet 86 of thesecondary air flowpath 78. It is further contemplated and understoodthat the air scoop assembly 72 may be generally mounted on any surfacethat defines at least in-part a primary air flowpath and where theretrieval of a secondary air flow is required.

In operation, and with the flow control device 80 in a substantiallyopen position, bypass air flows generally in an axially downstreamdirection (see the bypass airstreams shown as arrows 90 in FIG. 3) alongthe bypass flowpath 29. A portion of this bypass air is scooped-up bythe hood 74 of the air scoop assembly 72 and flows through or along thesecondary air flowpath 78. With the flow control device 80 substantiallyopen, no (or minimal) air vortices are created about the hood whichcould hinder efficient flow of the bypass airstreams 90. Absent thefeatures of the present disclosure, with the flow control device closedor substantially closed, no (or minimal) secondary air flows through thesecondary air flowpath and the hood of the air scoop assembly mayfunction more as an airstream obstruction in the bypass flowpath. Assuch and in more traditional designs, air vortices or disturbances maybe created that undesirably disrupt the bypass airstreams 90, reduceairflow efficiency, and lead to undesired resonance that may producesignificant unsteady pressures resulting in elevated noise and elevatedunsteady stresses in surrounding structures, if not properly controlled.

Referring to FIGS. 3 and 4, the irregular or scalloped shape of theleading edge 82 of the hood 74 generally functions as a plurality ofvortex generators that create, controlled, air vortices 92 generallywhen the flow control device 80 is closed, and which stem from theleading edge 82 of the hood 74 and generally co-extend in the downstreamdirection with the bypass airstreams 90 thereby minimizing anydisruption of the bypass air flow. That is, with the flow control device80 generally closed, there is a continuous shedding of streamwisevorticity. The “continuous shedding” is desirable over discontinuous orperiodic shedding because it eliminates the production of undesiredresonance that produce excessive noise in the duct and stress uponsurrounding structure. That is, the irregular or non-uniform edge 82avoids the tendancy to shed a full-width coherent vortex and avoids anycoupling with the natural frequency of the cowlings 62, 64. In additionto breaking up any full-width coherent vortex, with the valve 80 closed,the non-uniform edge 82 acts as vortex generators in the flow spillingaround the edge, shedding continuous, streamwise, vorticity and reducingany flow separation in the bypass air flowpath 29 downstream of the hood74. It is further understood and contemplated that the irregular shapeof the leading edge may not be scalloped but may take the form of anyvariety of shapes that may produce air vortices as described.

Referring to FIGS. 4 and 5, the irregular shape of the leading edge 82may be a plurality of scallops 94 (i.e. each scallop generally being onevortex generator). Each scallop 94 meets the next adjacent scallop at anapex or convex portion 96 that generally projects and substantiallyfaces in an upstream direction, and which contributes toward theshedding of the air vortices 92. Each apex 96 is spaced from the nextadjacent apex by a distance 100. Each scallop 94 also has a concaveportion 98 that substantially faces in the upstream direction and isgenerally spaced axially (with respect to the engine axis A) from theapex 96 by a distance 102. The hood 74 has a width 104 measured betweenthe joinder(s) of the hood 74 to the surface 84 of the core cowling 62,and a height 106 that is generally the maximum projection of the hoodinto the bypass air flowpath 29 (i.e. maximum radial distance from thesurface 84 to the hood 74). The width 104 is substantially greater thanthe height 106, and the height 106 is generally two to five timesgreater than the distance 100 between apexes 96.

Axially downstream of the leading edge 82, the hood 74 has a generalthickness 108 and the concave portion 98 may have a parabolic shapedcross section that generally begins where the hood has the thickness 108and projects upstream to a vertex by a distance 110 that may besubstantially equal to thickness 108. The apex or convex portion 96 mayhave a parabolic shaped cross section similar to the concave portion 98but generally more pointed (i.e. more tapered). The distance 102 betweenthe apex 96 and the concave portion 98 may be about equal to twice thethickness 108.

It is understood that relative positional terms such as “forward,”“aft,” “upper,” “lower,” “above,” “below,” and the like are withreference to the normal operational attitude and should not beconsidered otherwise limiting. It is also understood that like referencenumerals identify corresponding or similar elements throughout theseveral drawings. It should be understood that although a particularcomponent arrangement is disclosed in the illustrated embodiment, otherarrangements will also benefit. Although particular step sequences maybe shown, described, and claimed, it is understood that steps may beperformed in any order, separated or combined unless otherwise indicatedand will still benefit from the present disclosure.

The foregoing description is exemplary rather than defined by thelimitations described. Various non-limiting embodiments are disclosed;however, one of ordinary skill in the art would recognize that variousmodifications and variations in light of the above teachings will fallwithin the scope of the appended claims. It is therefore understood thatwithin the scope of the appended claims, the disclosure may be practicedother than as specifically described. For this reason, the appendedclaims should be studied to determine true scope and content.

What is claimed is:
 1. An air scoop assembly configured to mount to asurface defining a primary flow path, the air scoop assembly comprising:a hood having an irregular upstream edge and configured to project intothe primary flowpath.
 2. The air scoop assembly set forth in claim 1,wherein the edge is at least one vortex generator.
 3. The air scoopassembly set forth in claim 2, wherein the edge is scalloped.
 4. The airscoop assembly set forth in claim 2 further comprising: an air ducthaving an inlet defined at least by the surface and the edge.
 5. The airscoop assembly set forth in claim 4, wherein the air duct defines asecondary flowpath in fluid communication with the primary flowpath andfor the intermittent flow of air from the primary flowpath.
 6. The airscoop assembly set forth in claim 5 further comprising: a valveconfigured for the intermittent isolation of the secondary flowpath. 7.The air scoop assembly set forth in claim 6, wherein the valve includesa closed position and an open position and the at least one vortexgenerator forms at least one vortices that breaks up any coherentshedding off of air flow from the hood when the valve is in the closedposition.
 8. The air scoop assembly set forth in claim 2, wherein theedge has at least one apex projecting in an upstream direction and intothe primary flowpath.
 9. The air scoop assembly set forth in claim 7,wherein the edge has at least one apex projecting into an upstreamdirection and into the primary flowpath.
 10. The air scoop assembly setforth in claim 9, wherein the hood is flush with the surface.
 11. Theair scoop assembly set forth in claim 9, wherein the hood projectstransversely into the primary flowpath and outward from the surface. 12.The air scoop assembly set forth in claim 9, wherein the surface iscarried by a nacelle.
 13. The air scoop assembly set forth in claim 8,wherein the apex projects upstream by a downstream-most portion of theedge by a distance that is about twice a thickness of the hood.
 14. Theair scoop assembly set forth in claim 8, wherein the at least one apexis spaced from a next adjacent apex by a distance that is about onefifth to about one half a height of the hood.
 15. A nacelle for a gasturbine engine comprising: a fan cowling concentrically disposed to anengine axis and surrounding a fan section of the gas turbine engine; acore cowling concentrically disposed to the engine axis and locateddownstream of the fan section with an annular air bypass flowpathdefined between and by the fan and core cowlings; and a hood formed tothe core cowling and projecting into the bypass flowpath, the hoodincluding a leading edge that includes at least one apex projecting inan upstream direction and acting as at least one vortex generator. 16.The nacelle set forth in claim 15 further comprising: an air duct havingan inlet defined at least by the core cowling and the edge; and whereinthe air duct defines a secondary flowpath in fluid communication withthe bypass flowpath and for the intermittent flow of air from the bypassflowpath.
 17. The nacelle set forth in claim 16 further comprising: avalve in the air duct for the intermittent isolation of the secondaryflowpath; and wherein the valve includes a closed position and an openposition and the at least one vortex generator forms at least one vortexthat breaks up any coherent shedding off of air flow from the hood whenthe valve is in the closed position.
 18. The nacelle set forth in claim15, wherein the hood is flush with the core cowling.
 19. The nacelle setforth in claim 15, wherein the hood projects transversely into thebypass flowpath and radially outward from the core cowling.
 20. A methodof operating an air scoop assembly comprising the steps of:substantially closing the air scoop assembly having a hood that projectsinto a primary air flowpath; and forming at least one air vortex thatstems from an irregular leading edge of a hood of the air scoop assemblyand extends in a substantially downstream direction thereby minimizingdisruption of airstreams in the primary air flowpath.